#pragma region CPL License
/*
Nuclex Native Framework
Copyright (C) 2002-2021 Nuclex Development Labs

This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 of the
License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
IBM Common Public License for more details.

You should have received a copy of the IBM Common Public
License along with this library
*/
#pragma endregion // CPL License

#ifndef NUCLEX_STORAGE_FILESYSTEM_LINUX_LINUXFILEAPI_H
#define NUCLEX_STORAGE_FILESYSTEM_LINUX_LINUXFILEAPI_H

#include "Nuclex/Storage/Config.h"

#if defined(NUCLEX_STORAGE_LINUX)

#include <string> // std::string
#include <cstdint> // std::uint8_t and std::size_t

#include <sys/stat.h> // ::fstat() and permission flags
#include <dirent.h> // struct ::dirent

namespace Nuclex { namespace Storage { namespace FileSystem { namespace Linux {

  // ------------------------------------------------------------------------------------------- //

  /// <summary>Wraps the Linux file system API</summary>
  /// <remarks>
  ///   <para>
  ///     This is just a small helper class that reduces the amount of boilerplate code
  ///     required when calling the file system API functions, such as checking
  ///     result codes over and over again.
  ///   </para>
  ///   <para>
  ///     It is not intended to hide operating system details or make this API platform
  ///     neutral (the File and Container classes do that), so depending on the amount
  ///     of noise required by the file system APIs, only some methods will be wrapped here.
  ///   </para>
  /// </remarks>
  class LinuxFileApi {

    /// <summary>Creates the specified directory</summary>
    /// <param name="path">Path to the directory that will be created</param>
    public: static void MakeDirectory(const std::string &path);

    /// <summary>Creates all directories down to the specified path</summary>
    /// <param name="directory">Directory that will be created recursively</param>
    public: static void MakeDirectoryRecursively(const std::string &directory);

    /// <summary>Deletes a directory and everything in it</summary>
    /// <param name="path">Path of the directory that will be deleted</param>
    public: static void RemoveDirectory(const std::string &path);

    /// <summary>Deletes a file</summary>
    /// <param name="path">Path of the file that will be deleted</param>
    public: static void RemoveFile(const std::string &path);

    /// <summary>Returns the current working directory of the process</summary>
    /// <returns>The process' current working directory</returns>
    public: static std::string GetCurrentWorkingDirectory();

    /// <summary>Retrieves the protection mode of the file in the specified path</summary>
    /// <param name="path">Path of the file whose protection mode will be retrieved</param>
    /// <returns>The protection mode of the specified file</returns>
    public: static ::mode_t StatMode(const std::string &path);

    /// <summary>Retrieves the status of the file in the specified path</summary>
    /// <param name="path">Path of the file whose status will be retrieved</param>
    /// <param name="fileStatus">Receives the file status on successfull execution</param>
    /// <returns>True if the file exists and was queried, false if it doesn't exsit</returns>
    /// <remarks>
    ///   If any error other than the file not existing occurs, an exception is thrown.
    /// </remarks>
    public: static bool Stat(const std::string &path, struct ::stat &fileStatus);

    /// <summary>Attempts to opens the specified file for shared reading</summary>
    /// <param name="path">Path of the file that will be opened</param>
    /// <param name="fileDescriptor">
    ///   Receives the file descriptor (numeric handle) of the opened file on success
    /// </param>
    /// <returns>
    ///   True if the file was opened, false if any error occurred and the contents
    ///   of the <see cref="fileDescriptor" /> parameter should not be used.
    /// </returns>
    /// <remarks>
    ///   Use this if you need to read files that may be missing or that you may not be
    ///   permitted to read and where you wish to fall back to something else in that case.
    /// </remarks>
    public: static bool TryOpenFileForReading(const std::string &path, int &fileDescriptor);

    /// <summary>Opens the specified file for shared reading</summary>
    /// <param name="path">Path of the file that will be opened</param>
    /// <returns>The descriptor (numeric handle) of the opened file</returns>
    public: static int OpenFileForReading(const std::string &path);

    /// <summary>Creates or opens the specified file for exclusive writing</summary>
    /// <param name="path">Path of the file that will be opened</param>
    /// <returns>The descriptor (numeric handle) of the opened file</returns>
    public: static int OpenFileForWriting(const std::string &path);

    /// <summary>Moves the file cursor for the specified file</summary>
    /// <param name="fileDescriptor">File whose file cursor will be moved</param>
    /// <param name="location">Location the file cursor will be moved to</param>
    /// <returns>The actual location the file cursor</returns>
    public: static std::uint64_t Seek(int fileDescriptor, std::uint64_t location);

    /// <summary>Determines the file status of a file by its handle</summary>
    /// <param name="fileDescriptor">Handle of the file whose status will be determined</param>
    /// <param name="fileStatus">Receives the file status</param>
    public: static void Stat(int fileDescriptor, struct ::stat &fileStatus);

    /// <summary>Reads data from the specified file</summary>
    /// <param name="fileDescriptor">Handle of the file from which data will be read</param>
    /// <param name="buffer">Buffer into which the data will be put</param>
    /// <param name="count">Number of bytes that will be read from the file</param>
    /// <returns>The number of bytes that were actually read</returns>
    public: static std::size_t Read(
      int fileDescriptor, std::uint8_t *buffer, std::size_t count
    );

    /// <summary>Reads data from the specified file</summary>
    /// <param name="fileDescriptor">Handle of the file from which data will be read</param>
    /// <param name="offset">Offset in the file from which data is read</param>
    /// <param name="buffer">Buffer into which the data will be put</param>
    /// <param name="count">Number of bytes that will be read from the file</param>
    /// <returns>The number of bytes that were actually read</returns>
    public: static std::size_t PositionalRead(
      int fileDescriptor, std::uint64_t offset, std::uint8_t *buffer, std::size_t count
    );

    /// <summary>Writes data into the specified file</summary>
    /// <param name="fileDescriptor">Handle of the file into which data will be written</param>
    /// <param name="buffer">Buffer containing the data that will be written</param>
    /// <param name="count">Number of bytes that will be written into the file</param>
    /// <returns>The number of bytes that were actually written</returns>
    public: static std::size_t Write(
      int fileDescriptor, const std::uint8_t *buffer, std::size_t count
    );

    /// <summary>Writes data into the specified file</summary>
    /// <param name="fileDescriptor">Handle of the file into which data will be written</param>
    /// <param name="offset">Offset in the file at which data is written</param>
    /// <param name="buffer">Buffer containing the data that will be written</param>
    /// <param name="count">Number of bytes that will be written into the file</param>
    /// <returns>The number of bytes that were actually written</returns>
    public: static std::size_t PositionalWrite(
      int fileDescriptor, std::uint64_t offset, const std::uint8_t *buffer, std::size_t count
    );

    /// <summary>Closes the specified file</summary>
    /// <param name="fileDescriptor">Handle of the file that will be closed</param>
    /// <param name="throwOnError">
    ///   Whether to throw an exception if the file cannot be closed
    /// </param>
    public: static void Close(int fileDescriptor, bool throwOnError = true);

    /// <summary>Opens a directory for enumeration</summary>
    /// <param name="path">Path of the directory that will be opened</param>
    /// <returns>The opened directory</returns>
    public: static DIR *OpenDirectory(const std::string &path);

    /// <summary>Reads the next directory entry from a directory</summary>
    /// <param name="directory">Directory from which the next entry will be read</param>
    /// <returns>
    ///   The next directory entry or NULL if the last directory entry has been reached
    /// </returns>
    public: static struct ::dirent *ReadDirectory(::DIR *directory);

    /// <summary>Closes a directory that was opened for enumeration</summary>
    /// <param name="directory">Directory that will be closed</param>
    /// <param name="throwOnError">
    ///   Whether to throw an exception if the directory cannot be closed
    /// </param>
    public: static void CloseDirectory(::DIR *directory, bool throwOnError = true);

    /// <summary>Reads the target file or directory pointed to by a symlink</summary>
    /// <param name="path">Path to the symlink whose target will be read</param>
    /// <returns>The path to which the symlink is pointing</returns>
    public: static std::string ReadLink(const std::string &path);

    /// <summary>Resolves a path, following symlinks, to its ultimate target</summary>
    /// <param name="path">Path that will be resolved to its ultimate target</param>
    /// <returns>The ultimate target of the specified path</returns>
    public: static std::string RealPath(const std::string &path);

  };

  // ------------------------------------------------------------------------------------------- //

  /// <summary>Closes a directory handle upon destruction</summary>
  class DirectoryScope {

    /// <summary>Initializes the directory handle closer</summary>
    /// <param name="directoryHandle">Directory handle that will be closed</param>
    public: DirectoryScope(::DIR *directoryHandle) :
      directoryHandle(directoryHandle) {}

    /// <summary>Closes the directory handle</summary>
    public: ~DirectoryScope() {
      const bool throwOnError = false;
      LinuxFileApi::CloseDirectory(this->directoryHandle, throwOnError);
    }

    /// <summary>Directory handle that will be closed upon destruction</summary>
    private: ::DIR *directoryHandle;

  };

  // ------------------------------------------------------------------------------------------- //

  /// <summary>Closes a file upon destruction</summary>
  class FileScope {

    /// <summary>Initializes the file closer</summary>
    /// <param name="fileDescriptor">File that will be closed</param>
    public: FileScope(int fileDescriptor) :
      fileDescriptor(fileDescriptor) {}

    /// <summary>Closes the file</summary>
    public: ~FileScope() {
      const bool throwOnError = false;
      LinuxFileApi::Close(this->fileDescriptor, throwOnError);
    }

    /// <summary>File that will be closed upon destruction</summary>
    private: int fileDescriptor;

  };

  // ------------------------------------------------------------------------------------------- //

}}}} // namespace Nuclex::Storage::FileSystem::Linux

#endif // defined(NUCLEX_STORAGE_LINUX)

#endif // NUCLEX_STORAGE_FILESYSTEM_LINUX_LINUXFILEAPI_H